1. Field of the Invention
This invention relates to a fire-resistant glazing consisting of at least two glass sheets held apart and parallel to one another between which is disposed a layer of a hydrogel, the aqueous phase of which contains a dissolved salt.
2. Description of the Prior Art
Fire-resistant glass panels of this type are known from DE 27 13 849 C2. Their method of functioning in case of fire consists in that, initially, the heat arising is absorbed by the water in the hydrogel layer and is consumed by evaporating the water, and that, after the water has been evaporated and after the solid organic phase of the hydrogel has been burnt, a solid, foam-like structure is formed from the salt. This foam-like solid structure is retained even under intense heat action and forms an insulating heat shield, which continues to impede the passage of the heat radiation. With this fundamental construction, fire-resistant glazings can be produced which satisfy the fire resistance classes G and the fire resistance classes F as defined in DIN 4102, part 5, of Sept. 1977.
In the known fire-resistant glass panels of the initially mentioned type, the polymer forming the solid phase of the hydrogel comprises a polyacrylamide, which is formed in aqueous solution by polymerization of methacrylamide and acrylamide. The polymerization takes place after the addition of peroxides or per-salts, with addition of an acceleration agent and, possibly, a cross-linking agent.
It is well known that acrylamide is a toxic compound, and its use for the production of fire-resistant glass panels is therefore not entirely harmless.